For example, as disclosed in JP 2011-124269 A, an ignitor semiconductor device for controlling a semiconductor switching element to be turned on or off to ignite a spark plug of an internal combustion engine is conventionally known. In the device disclosed in JP 2011-124269 A, the temperature of the semiconductor switching element is detected using a current signal obtained through a diode by utilizing temperature characteristic of the diode, which is used for overheat protection.